1. Field of the Invention
The present invention relates in general to hollow wire used in the construction of jewelry, and relates in particular to a method and apparatus for forming hollow wire links for constructing jewelry rope chains.
2. Description of Prior Developments
Jewelry rope chain is produced by forming precious metal wire into individual links and then interconnecting the links in a known fashion to form a helical chain. Examples of such chains and their construction are provided in U.S. Pat. Nos. 5,537,812, 5,660,036 and 5,303,540.
In some cases, it is desirable for form a series of flat reflective surfaces along the chain links to enhance the light reflecting characteristics of the chain. Diamond cutting tools and diamond grinding wheels are used to form such flat faceted surfaces and produce what is known as xe2x80x9cdiamond cutxe2x80x9d jewelry chains. An example of such diamond cut jewelry rope chain is disclosed in U.S. Pat. No. 5,285,625.
A problem arises when hollow wire is used to form diamond cut jewelry chains. Although hollow wire is desirable because it reduces the amount of precious metal required to form a rope chain, the resulting thin walls of the hollow chain links can be perforated during the diamond cutting of the facets in the thin walls. This penetration of the faceted surface through the thin hollow links forms a hole that ruins the rope chains.
Accordingly, a need exists for a hollow wire for forming hollow rope chain links and other articles of jewelry, including machine and hand made chains, and which allows full faceting without the risk of penetrating the link during diamond cutting of a facet.
A further need exists for a method and apparatus for forming hollow rope chain having a thickened wall portion particularly adapted for faceting by a diamond cutting operation.
The present invention has been developed to fulfill the needs noted above and therefore has as an object the provision of a method and apparatus for forming a hollow wire particularly adapted for producing diamond cut faceted surfaces such as used in jewelry rope chain links.
Another object of the invention is the provision of a hollow wire having internal and external mechanically worked surfaces formed by drawing a solid wire through a die.
Another object of the invention is the provision of a die having a groove forming element adapted to form an open internal groove in a solid wire so as to produce a thick walled section in a hollow wire.
Still another object of the invention is the provision of a hollow chain link particularly adapted for forming faceted diamond cut rope chains.
These and other objects are met by the present invention which is directed to a method and apparatus for forming hollow wire and hollow chain links adapted for producing diamond cut faceted jewelry rope chains. A wire drawing die is formed with a conical bore defining a wire drawing channel. A groove forming element such as a hard wire rod is mounted in the channel.
As a solid wire of soft precious metal, such as gold or silver, is drawn through the die, the groove forming element forms an axially-extending longitudinal groove along one side of the drawn hollow wire. The remaining solid section of the drawn wire is formed with a central thick-walled portion particularly adapted for faceting. A pair of thin-walled sections extend circumferentially from the central thick-walled portion so as to embrace and surround the drawn groove. Diamond cut facets can be formed in the central thick-walled portion of the chain links formed by the hollow wire. Such facets can be identical to those formed in conventional solid wire but by using a hollow wire, the hollow links can weigh up to 50% less than solid wire links.
The aforementioned objects, features and advantages of the invention will, in part, be pointed out with particularity, and will, in part, become obvious from the following more detailed description of the invention, taken in conjunction with the accompanying drawings, which form an integral part thereof.